1. Field of the Invention
The present invention relates to an optical fiber distribution module for connecting or exchanging connections of multi-core optical fibers, a single-fiber optical cord and a set-type optical fiber cords, and an optical fiber distribution system for managing operating information of a network connecting outdoor optical facilities with optical communication equipment in a telecommunication equipment center so that the system may be operated at its peak efficiency.
2. Description of the Related Art
Conventional optical fiber distribution module has a connection board with an array of connector adaptors, and a holding board for storing those fiber cords with connector plugs that are not in use, and connections or switching requires the following three basic operations.
(1) Connect a plug of a stored optical fiber cord to a desired adaptor on the connection board. PA1 (2) Change a connection by disconnecting a plug from the connection board and connecting it to another adaptor. PA1 (3) Disconnect a plug connected to an adaptor on the connection board and store the plug on the holding board. PA1 (1) Entangled cords are hard to handle and the effective length becomes too short to reach the desired location of the adaptor; PA1 (2) The weight of many fiber cords hanging from each other tends to load the fiber cord to distort the shape of the optical fiber inside the cord; and PA1 (3) The force applied to a fiber is transmitted to the connection section of the plug attached to the end of the cord to increase optical signal attenuation; thus resulting in difficulty of achieving higher fiber density for the optical fiber distribution module.
However, when such operations are repeatedly performed, many fiber cords become tangled, such that
Also, in some case, a set-type fiber cords, such as optical cable, are used for distribution of light signals on the fiber distribution board.
A set-type fiber cord is produced by bundling a plurality of fiber units, each unit containing several fiber cords.
Such set-type fiber cords are given identifying markings to enable to identify individual fiber cords within the cord unit, and such markings may be imprinted directly on the sheath for the cord, or indicated on a ring attached to the cord.
With the expansion of the optical fiber communication network, needs for switching the tangled fibers arise frequently, and a serious fiber congestion is experienced in the vicinity of the fiber sorting board, which is used to retain individual cords of the set-type fiber cords by the congregation of in-use fibers and not-in-use fibers which are stored in the holding board. Therefore, it is essential that individual fiber cords be clearly identifiable, particularly for the set-type fiber cords.
However, conventional set-type fiber cords allows identification of individual fiber cords within a given cord unit, but because the markings are the same for different units, it has been difficult to identify a particular fiber cord when the fiber units are debundled.
Especially, when such set-type fiber cords are used for fiber distribution purposes, fiber connections and fiber switching are made to different locations on the connection board on the basis of individual fibers, the bundle must be released before any particular fiber can be connected or switched to a specific adaptor.
Also, in equipment centers in a high density optical network, external fibers must be connected to internal fibers within the center using fiber termination modules (FTMs); and a distribution system is used to mange such fiber connections inside the centers.
Some examples of conventional FTMs will be presented in the following.
In general, FTMs are installed at the connection points between outdoor optical fiber cables in the subscriber loops and the indoor optical fiber cables in the central office. Examples of the conventional FTMs are reported in references (N. Tomita et al; "High-Speed & High-Capacity Technologies of Optical Fiber Line Testing System", TECHNICAL REPORT OF IEICE (THE INSTITUTE OF ELECTRONICS INFORMATION AND COMMUNICATION ENGINEERS), CS95-50, pp59-66).
FIG. 29 shows an example of the configuration of the center equipment including the conventional FTM. The system comprises: FTM 1; optical coupler 2; fiber selector (FS); test light introducing fibers 4 to the optical coupler 2; optical splitter 5; center-side optical filter 6; center communication equipment 7; center imaging equipment 8; transmission equipment units 9; star coupler units 10; test equipment modules 11; test instruments 12; fiber testing and equipment selection apparatus (FTES) 13; FS master-side optical fiber 14; fist indoor optical fiber cable 15; second indoor optical fiber cable 16; subscriber optical fiber cable 17; user-side optical filter 18; user-side data terminating unit 19; and user-side image terminating unit 20.
FIG. 29 shows a communication service system used for transmission of data and images. To provide high reliability, the equipment centers are provided with FTMs 1, transmission equipment units 9, star coupler modules 10, and TEMs 11.
Center communication equipment 7 used for data communication operate on signal light of a 1.3 .mu.m band and a 1.55 .mu.m band for imaging signals output from center image equipment 8 are injected in the star coupler module 10 through the first internal fiber cable 15. The optical splitter 5 in the star coupler 10 wavelength multiplexes the 1.3 .mu.m and 1.55 .mu.m band signals, and wavelength multiplexed signal is distributed to a plurality of output ports. Signal light output from the ports of the splitter 5 is input in the FTM 1 through the second internal cable 16. Signal light input in the FTM 1 passes through the optical coupler 2 which multi/demultiplexes test light, and is wavelength multiplexed to user-side data terminating unit 19 and user-side image terminating unit 20 through the subscriber cable 17, to be delivered as data and image transmission service.
Tests to be conducted from the equipment center when installing or maintaining optical cable will be explained in the following. The fiber selector 3 in the fiber test module 1 selectively couples test light splitting fibers 4 and the fiber selector master-side fiber 14 connected to the test apparatus 12 in the test equipment module 11. The fiber testing and equipment selection apparatus 13 in the FEM 11 selects the optical pulse tester in the test apparatus 12. By this process, test light from the optical pulse tester is injected in the subscriber cable 17, and signal loss distribution measurements and problem location searching are performed.
When performing the tests, to prevent test light from entering in the user-side data terminating unit 19 and user-side image terminating unit 20, the user-side optical filter 18 for blocking the test light and transmitting the signal light is disposed just ahead of the user-side data terminating unit 19 and the user-side image terminating unit 20. Also, to prevent test light and reflected light of the 1.55 .mu.m band output from the center image equipment 8 from entering in the center communication equipment 7, a center-side optical filter 6 for blocking test light and 1.55 .mu.m band light and transmitting the 1.3 .mu.m signal light is disposed in the signal light input port.
FIG. 31 shows an example of configuration of the conventional FTM 1, and those parts that correspond to FIG. 29 are referred to by the same reference numerals. The FTM 1 includes an excess cord length holder 21, and an excess cable length storage shelves 22, and on the left of FTM 1, there are optical couplers 2 in each shelf, and the test light splitting fibers 4 separated from each coupler 2 are connected to FS 3 disposed at the bottom section. On the right side, there is an excess cable length storage space having an excess cable length holder 21 and an excess cable length shelves 22 for storing excess cable length of primarily second optical fibers 16.
FIG. 32 shows the structure of a connection section in the conventional FTM 1, and those parts that are the same as those in FIGS. 29, 30 are referred to by the same reference numerals. It includes: optical connector adaptor 23; optical connector 24; single core tape connection section 25. A single-core tape connection section 25 and optical connector 24 are attached to the optical coupler 2.
When transmission service is to be commenced, subscriber cable 17 and FS master side fiber 14 are connected to the coupler 2. Next, the optical connector 24 of the second internal fiber cable 16 is connected to the optical connector adaptor 23 connected to the coupler 2, thereby commencing transmission service.
With increasing access to optical network, more optical fibers are needed to meet the demand of subscribers, and the service centers are required to increase the number of cable per unit floor area in the center. Also, the cable connections are closely meshed for connecting center equipment modules (on-fiber- transaction modules, OLT, modules), star coupler modules and FTM modules. The congestion of cable presents serious operational and maintenance problems.
Also, the lengths of the second internal cable 16 for connecting from the excess cable length assigning holder 21 to the optical coupler 2 are not uniform, excess cable length is inevitably created for the second internal cable 16, and a high cable density in the FTM cannot be achieved without solving the problem posed by excess cable length.
In the conventional FTM, the excess cable length holder 21 and excess cable length storage shelves 22 are used to store excess lengths of second internal cable 16. For new installations and repair of existing optical network, in-use fibers must be separated and untangled from other fibers for switching and connecting operations, and this aspect of the operation was extremely laborious and time-consuming.